Metabolic Abnormalities in Hispanic Children With Cystic Fibrosis

Our specific aims include:

1. AIM 1. Characterization of glucose tolerance, nutritional and clinical status, socioeconomic status, family history of diabetes and genotype in Hispanic CF children compared to Caucasian CF children. Each child will undergo a two-hour oral glucose tolerance test and will be categorized by glucose tolerance according to standards set forth by the 1998 CF Consensus Conference on Diabetes. Nutritional status will be determined by three-day food journals and intake will be compared to energy needs measured by indirect calorimetry. Socio-economic status will be calculated from reported family income and medical insurance coverage. Genotyping will be done at the laboratory of Dr. Arthur Beaudet at Baylor College of Medicine. Clinical status will be measured using modified NIH scores. Family history for both type 1 and type 2 diabetes will be obtained in Spanish by Dr.Vanderwel. This specific aim tests the hypothesis that glucose intolerance /frank CF related diabetes occurs at a younger age in Hispanics than in Caucasians with CF, and is correlated to family history of diabetes and clinical status.
2. AIM 2. Characterization of insulin secretion and insulin sensitivity. Previous studies in adults have described peripheral insulin resistance as a major cause of CF related diabetes, yet studies have not been conducted in children. Studies in adults and children without CF suggest that insulin resistance occurs more frequently in Hispanics. We will measure insulin secretion and insulin sensitivity using the frequently sampled intravenous glucose tolerance test (IVGTT) and the minimal model analysis of Bergman, as modified for children. This specific aim tests the hypothesis that Hispanic children with CF have worse peripheral insulin resistance, but similar insulin secretion when compared to Caucasian children with CF.
3. AIM 3. Quantification of post-absorptive gluconeogenesis and whole body protein turnover. Total hepatic glucose production (HGP) will be measured using [6,6-2H2]glucose. We will quantify gluconeogenesis by measurement of the incorporation of 2H into the 2nd, 5th and 6th carbons of glucose following 2H20 administration method of Landau). We will determine whole body protein turnover using the stable isotopes [1-13C]leucine and will measure serum amino acid levels. This specific aim tests the hypothesis that gluconeogenesis and whole body protein turnover are disproportionately higher in Hispanic children and adolescents with CF than in Caucasian CF children.